Modern buildings are often designed with a complete glass frontage. The "all glass" buildings use the same glass, often solar reflecting glass, for constant visual effect across the aspects of the building. However, the building is made up of vision glass (i.e. see through glass) and spandrel glass (i.e. glass which covers the building structure), The problem with spandrel glass is that it must look the same as vision glass during daylight hours to ensure the architect's visual design requirements for the building are met. The spandrel glass provides a panelling, for example, between floors to hide the structure of the building. As a consequence, the spandrel glass is subjected to harsh environmental conditions including direct exposure to UV light and, because of the lack of ventilation, glass temperatures of 100.degree. C. and more during exposure by the sun. During the night hours the glass temperature may fall to -10.degree. C. or lower, depending on ambient atmospheric conditions.
Various types of spandrel glasses have been used. For example, it may be a single sheet or a hermetically sealed insulating glass unit with an enamel coating on the inner side and an insulating glass panel behind. The disadvantages of insulating glass units are high cost, weight and appearance. Changes in temperature or pressure flex the glass and visible distortion in reflective images can occur.
Single glass panels can be enamelled particulary for solid colours. However, the architectual trend is towards all glass solar reflecting walls. This mirror type glass cannot be enamelled. Polyethylene film can be heat bonded to solar reflecting glass. However, although it can be effective, it is very difficult to apply the polyethylene without air bubbles. Other ways of overcoming the problem include the use of insulating foam or mineral wool closely adjacent to the glass. The main disadvantage of the latter systems is that under certain lighting conditions light passage can occur giving a non-pleasing effect to the outside of the building. In addition, the insulation can be displaced, volatile deposits or condensation staining can occur and damage the mirror surface spoiling the visual effect of the building.
GB1394206 (corresponding to U.S. Pat. No. 3,888,815) describes a two package room temperature vulcanizable composition which is useful as a roof coating material. During such use the two parts of the composition are mixed and applied to the roof by means of a spray gun. On mixing and application to the roof the material cures providing protection to the roof. The material successfully bonds to materials such as aluminium concrete, wood and stainless steel. In use, the thickness or bulk of composition also provides protection not only to the roof but also to the bond between the roof and the bulk of the material.
U.S. Pat. No. 3,813,364 describes a self-bonding heat vulcanizable silicone rubber composition which is self-bonding to various substrates such as plastics, metals or glass.
GB1278798 and GB1381933 describes silicone rubber compositions which are curable at moderate temperatures to produce a silicone rubber which bonds strongly to surfaces with which it is in contact with during curing.
The present invention attempts to provide a coating which can be attached or bonded to a translucent material and in particular to solar reflecting glass on the inside of the glass when in use. The coating will need to meet extreme bonding requirements as the bond of the coating to the substrate will be exposed to extremes of, for example, temperature and UV light without the protection of the bulk of the coating. The purpose of the bulk of the coating is to provide consistent opacity to the translucent material.
According to the present invention, there is provided a curable silicone rubber composition and an opacifier present in 0.1% to 35% by weight of the organopolysiloxane contained in the silicone rubber composition.
The present invention also provides a curable silicone rubber composition and an opacifier present in 0.1% to 35% by weight of the organopolysiloxane contained in the silicone rubber composition, the silicone rubber being coated onto a translucent sheet material and cured.
In a further aspect, the present invention provides a method of coating a surface of a translucent material to stop light transmission by the translucent material, which method comprises applying the opaque curable silicone rubber composition to the translucent material and curing the silicone composition.
The silicone rubber composition may be a room temperature vulcanizable silicone rubber composition or may be a heat-curable silicone rubber composition.
The important aspect of the present invention is the opacifier further described below. In addition, filler may also be added to the composition.